The present invention is directed to a protective spark cover for a respirator filter. More particularly, the present invention is a cover to protect respirator filters from damage due to sparks and the like such as are generated by metal working operations.
Respirators are commonly employed to filter air inhaled by a user under hazardous breathing conditions such as in environments having noxious vapors or particulates suspended in the air. Conventional respirators include a face mask which covers the nose and mouth of the user. The mask has one or more inlet valves through which air is drawn as the user inhales and an outlet valve through which air exits the mask as the user exhales. One or more filters, either integral or detachable, are connected over the inlet valve so as to form a filtered air channel between the ambient atmosphere and the interior air passages of the face mask. Thus, as air is drawn into the face mask by the user, it passes through the filter(s) thus cleansing the air and enhancing the safety of the user.
It is important that such respirators provide high efficiency both with respect to filtering out a very high percentage of unwanted constituents (rejection efficiency) as well as with respect to minimizing the pressure drop required to pull air through the respirators. Typically, the high rejection efficiency is obtained by use of multiple layers of filter fabric. In order to minimize the pressure drop required to draw air through the filters, filtration elements with large surface areas have evolved. Examples of such modern high-efficiency filtration elements are included in U.S. Pat. No. 5,732,695, issued to Metzger and U.S. Pat. No. Re. 35,062, issued to Brostrom et al., both of which are incorporated herein by reference. Further, FIG. 1 herein depicts a typical modern respirator with two filter elements. Thus, as a result of the need for efficient respirators, modern respirator filters typically present large exposed surfaces of filter material.
One hazardous breathing situation in which respirators are used is in metal working operations, such as welding, metal smelting or cutting metals, and in similar situations in which sparks, molten metal splatter and similar ignition sources (generally referred to herein as xe2x80x9csparksxe2x80x9d) are generated. These sparks present a problem in the use of modern respirators, in that the filter fabrics used in respirator filters typically will readily melt or char when exposed to such sparks. Thus, use of respirators around metal welding, smelting, cutting, and other activities producing sparks, can damage exposed filter elements by contact of such sparks with the filter material. Further, mechanical damage can occur from airborne chips or particles, which may cut or tear the filter material. Such damage produces voids in the filter material which results in loss of filter rejection efficiency and in filter failure. In other words, the filter integrity is compromised without the wearer knowing that the rejection efficiency is less than is expected.
Some prior art filters have included a layer of flame retardant fabric as the outer layer of filter material. However, generally such flame retardant materials can melt or char when exposed to sparks and thus do not provide effective protection from sparks. Moreover, such materials to not protect the filter from mechanical damage caused by metal chips or other particles. Therefore, there is a need to provide protection of such filter elements from damage due to flying sparks, chips and the like. Moreover, it is crucial that while providing protection for such filter elements, that the primary function of the elements, to efficiently provide filtered air to the users, not be impaired by whatever protective device is applied to the filter. Further, it is desirable for cost reasons that such a protective spark cover is removable from the filter and reusable.
It is therefore an object of this invention to provide a protective spark cover for respirator filters to prevent damage from flying sparks and the like.
It is a related object of this invention to provide a protective spark cover for respirator filters which does not impede air flow in normal use of the filter.
In one aspect, it is an object of this invention to provide a protective spark cover for respirator filters which is removable and reusable.
It is a further object of this invention to provide a filter spark cover which is durable in use and easy to maneuver on and off the filter with a minimum of handling by the user.
These and other objects of the invention are met by a respirator filter protective spark cover comprised of a protective screen effective to suppress welding sparks and the like, which screen is fitted to a flexible frame. The frame is attached to the edge of the screen and configured to conform to and grasp an edge of the filter in a removable fashion, thus holding the screen over the exposed surface of the filter. Preferably the frame holds the screen a small distance away from the surface of the filter, so as to dissipate heat from the sparks without transmitting the heat to the surface of the filter.
In one embodiment, the protective spark cover has a flexible frame, preferably a flexible plastic or rubber material, which frame fits closely to an outer rigid ring on a common type of respirator filter.
In another embodiment, the protective spark cover is provided with extended tabs or the like to grasp the soft edges of another common type of respirator filter. The present invention also encompasses a protective spark cover made integral with a respirator filter.